There are known cruise control systems for vehicles, which make it possible to regulate the speed of the vehicle at a desired speed selected by the driver. If the vehicle has at least one distance sensor, e.g., in the form of a radar sensor, a stereo-camera system or the like, the vehicle speed may also be regulated in such a way that a suitable safety distance from a vehicle driving in front is automatically maintained. One example of such a control system, also known as an adaptive cruise control or ACC system, is described in the article “Adaptive Cruise Control System—Aspects and Development Trends” by Winner, Witte, Uhler and Lichtenberg, Robert Bosch GmbH, in SAE Technical Paper Series 961010, International Congress & Exposition, Detroit, Feb. 26-29, 1996.
However, complete detection and reliable evaluation of the traffic environment are still impossible with the available sensor devices, so these systems have in the past been suitable mainly for relatively stable traffic situations such as driving on a highway or an expressway. In city traffic or when driving at a low speed on a winding section of road, however, the uncertainties in detection of the particular relevant target object may result in an accident risk. For this reason, the ACC systems known in the past have been designed to be activated only above a certain limit speed.
There have already been proposals for expanding the range of applications of the ACC system to include a traffic situation known as stop-and-go traffic which occurs, for example, in traffic congestion or slow-moving traffic. This traffic situation is also relatively stable and is therefore suitable for automatic cruise control, but the functionality must be expanded to include automatic control of stop-and-go driving situations.
In addition, the range of applications of this stop-and-go function should be limited to speeds below a certain level, and the speed ranges for the ACC function and the stop-and-go function may overlap.
Since the regulation algorithms in the ACC mode designed for high driving speeds and the stop-and-go mode designed for low driving speeds are different, it is expedient for the transition between these two modes not to be automatic, but instead to depend on a command to be entered by the driver, so that the performance of the system as a whole remains transparent for the driver.
European Patent Application No. 992 387 describes a control and regulation method in which a stop-and-go mode is activatable only under certain conditions. One of these conditions is that the driving speed of one's own vehicle must be below a definable limit speed. If the conditions for stop-and-go mode are met, the system will first enter a standby state, which is displayed for the driver and is thus represented to the driver as a prompt to activate the stop-and-go mode. If the conditions for regulation in stop-and-go mode are no longer met, e.g., because the vehicle being pursued as a target object is temporarily lost from the detection range of the distance sensor, then the system enters a mode known as “coasting mode” in which the vehicle speed is reduced with moderate deceleration. The driver is able to shut down the regulation entirely either by input of a shutdown command or, if the conditions are met again, switch it back to stop-and-go mode. In addition, the driver has the option of switching to the normal control mode (ACC) if the conditions for this are met.